The present invention relates to an improved process for recording variable analog data representative of a plurality of physical parameters and to a sequential value multi-point recorder for recording such physical parameters in the form of continuous tracings on a recording paper.
Heretofore, multi-point recorders have been provided which are adapted to print a plurality of variable physical parameters on a chart. Such multi-record printing may be accomplished by use of a print wheel that is indexed for each measurement to bring into printing relation with the chart a type character selected to identify the variable being recorded. The print wheel is moved to a position along the chart corresponding to the instantaneous value of the variable being recorded and then is pressed thereagainst momentarily.
Each of the typed characters is made of a different form than the other characters. In some uses of the recorder, a single color is made use of, and in others, if desired, each character is printed in a different colored ink.
Such recorders may include an ink wheel pad or ribbon for inking the type characters on the type of print wheel. Such inking systems allow a single recording instrument to print in different colors for different characters to be employed. With this system, each type character is synchronized with the inking system so that each time a type character is selected, the proper color is also selected.
Such multi-record printing instruments generally provide for a measuring and print wheel balancing circuit comprising a plurality of separate transducers or thermo-couples each of which is employed to sense the magnitude of a variable condition under measurement such as temperature, pressure, voltage, or the like. A selector switch is provided to selectively cut in each input from the transducer or thermo-couples with a null balancing circuit which contains a balancing motor for driving the print wheel across the chart to a balanced position. When the print wheel is in this position, the magnitude of each of the variables under measurement in identifiable characteristic form can be separately printed on the chart by means of a print wheel cam-actuating printer mechanism.
A typical multi-record printing recorder of the construction described above is disclosed in U.S. Pat. No. 3,216,015 and requires that the balancing motor must move the printing wheel back and forth across the chart each time it senses the magnitude of a variable condition. This reciprocating movement of the printing wheel for printing each variable condition on the chart is time consuming, especially where it is desired to record a multiplicity of variable conditions. Additionally, such recorder systems are subject to a great amount of wear and tear in view of the constant movement of the recorder components including the multi-point contact switch; balancing motor; slide wire and contactor systems, and print wheel, for example. Thus, recorder systems of this nature do not have the desired reliability and require a high degree of maintenance to maintain all moving components in continuous operating condition over long periods of time.
In contrast to the multi-point recorder system disclosed in the above described U.S. Pat. No. 3,216,015, variable multi-point recorders have been provided which are adapted to produce recordings of a plurality of variable physical phenomena by sequentially scanning a plurality of input circuits and then producing indicia representative of the measured variable values. In that manner, a separate trace, usually a series of dots, is produced for each of the input signals, each trace being representative of a physical phenomena such as temperature, pressure, or the like. In these prior art recorders, a series of timed pulses is generated for controlling the recorder operation by employing a constant speed timing motor to drive a rotary switching arrangement. Here, the constant speed of the timing motor necessarily fixes the length of the recording cycle for each of the input points. Representative of such multi-point recorders is U.S. Pat. No. 3,576,582, issued on Apr. 27, 1971 to R. T. Smith, Jr. Here too, an excessive amount of time is expended in reciprocating a movable printing carriage across a recording sheet member for printing upon the sheet member a plurality of record traces to correspond to several input signals sensed. Thus, the time of producing indicia representative of a pluraltiy of measured variable values and printing them on the chart in a random fashion by value is excessive. Additionally, wear and tear of the constantly moving recorder components demand constant attention and maintenance.
An improvement in the multiple point recorder of U.S. Pat. No. 3,576,582 was obtained with the multiple point recorder described in U.S. Pat. No. 3,665,414, issued on May 23, 1972 to Fredrick S. Hutch, et al. In this recorder, the need for a timing motor was eliminated and by employing digital techniques, a more versatile means for programming the recorder operation was obtained. With the digital programming the speed of the recorder operation depends on the base frequency of the clock signal. Here too, however, the sequential scanning of the plurality of input circuits for producing indicia representative of the measured variable data values requires excessive movement of the print head in printing each variable value on the recording chart. Thus, the print head is still being directed to print out the measured variable values not in accordance with the magnitude of the variable valves but in accordance with the sequence in which the plurality of input circuits are scanned. Thus, in effect, the print head moves in a random fashion over the recording chart to print out each variable value each time a scanning function of the plurality input circuits is performed.
A further improvement in multi-point recording systems was achieved with the introduction of non-impact type printing heads. Visual information such as alpha-numeric characters or other symbols previously involved the use of printing types in the form of pins, or the like, which are pressed against the recording paper with a carbon tape, or the like, interposed therebetween to thereby impress the recording paper with the shapes of the printing types or the pins. Such systems are commonly referred to as "Impact Printers" and have been widely used because of their merit in obtaining high definition of the printing, availability of any desired shape of printed character, useability of ordinary paper for the recording paper, and freedom of the recorded information from aging. However, such mechanical print heads produce a considerable noise due to the impact of the printing types during impression. Additionally, the numerous mechanically movable parts of the print head mechanism are subject to considerable wear and tear during their uninterrupted use in printing information, such as variable values, on the recording paper. Such electro-mechanical print head mechanisms must be continuously monitored and serviced by skilled maintenance personnel to maintain the equipment in working order.
A solution to the problems inherent in electro-mechanical print heads became available with the introduction of thermal print heads used in combination with thermal-sensitive recording paper. Such thermal print heads utilize a plurality of thermal segments which are selectively caused to generate heat to thereby provide any desired pattern on the thermal-sensitive paper. Such thermal print heads have the advantage of eliminating the mechanical printing components used in prior electro-mechanical print heads and permit the introduction of more reliable electrical controls. An example of the use of a thermal print head in a recording device is represented by U.S. Pat. No. 3,754,279 which issued on Aug. 21, 1973 to Leo F. Valenti, et al.
Another example of a recording apparatus of the non-impact type is disclosed in U.S. Pat. No. 3,855,448 which issued on Dec. 17, 1974 to Takayoshi Hanagata, et al. In this non-impact type system, a plurality of heating segments on a thermal print head are generally disposed in a common plane and can be heated separately and selectively. The system employs a heat-sensitive print member composed of a heat-resistant back-up layer and a thin film of an adhesive resin of low melting point disposed over the back-up layer, and also employs a web of recording paper free of any thermal sensitive material. When the thermal print head and the recording paper are moved relative to each other in one direction, the print member is brought into intimate contact with both of the thermal print head and the recording paper. In such position, the islands in the thermal print head may be selectively energized to melt the adhesive resin in the resin film and transfer the molten resin to the recording paper, thus accomplishing a print on the recording paper.
Another thermal printing technique is disclosed in U.S. Pat. No. 3,840,878 issued on Oct. 8, 1974 to David T. Houston, et al.